The sure-click dial operates smoothly and ensures you have the right temp and tone. Tempo ranges from 40 - 216 BPM, with 0, 2-6 beats and 6 rhythms, plus an A2-C6 tone generator with a total of 40 notes. A440 - 445 Hz calibration. Volume adjusts from very loud to silent mode, with bright LEDs. Use an optional AC adaptor or 9V battery. Includes earphone jack and fold-out stand. 2 1/4" W x 1" D x 5 1/4" H.